es034324+_si_001.pdf (38.62 kB)
Products of Aqueous Chlorination of 17β-Estradiol and Their Estrogenic Activities
journal contribution
posted on 2003-12-15, 00:00 authored by Jianying Hu, Shuijie Cheng, Takako Aizawa, Yoshiyasu Terao, Shoichi KunikaneTo assess the estrogenic activity potentially stemming
from 17β-estradiol (E2) in drinking water, ESI-LC-MS was
used to identify the products of its aqueous chlorination under
the following conditions: 50 μg/L E2, 1.46 mg/L sodium
hypochlorite, pH 7.5, 25 °C. Seven products, including 2,4-dichloro-17β-estradiol, monochloroestrone, 2,4-dichloroestrone, and the four byproducts such as 4-[2-(2,6-dichloro-3-hydroxyphenyl)ethyl]-7α-methyloctahydroinden-5-one
(product C in the text) were identified in chlorinated E2
solution. The estrogenic activities of the aqueous chlorinated
E2 solution at 10, 30, 60, 120, and 180 min contact time
were assessed by a yeast two-hybrid system based on the
ligand-dependent interaction of two proteins, a human
estrogen receptor (ER) and a coactivator. All five solutions
elicited transcriptional activation induction. The maximal
β-galactosidase activities induced by the chlorinated solution
at 10, 30, and 60 min were similar and slightly lower
than those before chlorination, while the activities of the
chlorinated solution at 120 and 180 min were about 40% of
those before chlorination. Finally, 4-chloro-17β-estradiol (4-chloro-E2) (we failed to synthesize the 2-chloroestrone (2-chloro-E1)), 2,4-dichloro-17β-estradiol (2,4-dichloro-E2), and
2,4-dichloroestrone (2,4-dichloro-E1) were synthesized,
and product C was fractionated by HPLC. It was found that
4-chloro-E2 elicited strong estrogenic activity, at almost
the same level as that of estrone (EC50 = 102 nM), while 2,4-dichloro-E2 elicited weaker β-galactosidase activity
compared with that of 4-chloro-E2. The EC50 was ca. 103
nM. The maximal β-galactosidase activity for 2,4-dichloro-E1 was lower than that of 2,4-dichloro-E2, while its EC50
was similar to that of 2,4-dichloro-E2. In addition, product C,
4-[2-(2,6-dichloro-3-hydroxyphenyl)ethyl]-7α-methyloctahydroinden-5-one, induced high β-galactosidase
activity at the relatively higher concentration of 3.5 × 105
nM. On the basis of the dose−response curve of a
single byproduct of chlorinated E2, the estrogenic activity
at 120 and 180 min appears to be induced mainly by 2,4-dichloro-E2 and 2,4-dichloro-E1.